Method of cleaning and decolorizing shoes and other leather articles



Unitd tes Patent METHOD 9F CLEANING AND DECOLORIZING SHOES AND OTHERLEATHER ARTICLES Kristian Julius Simonsen, Nasbypark, Sweden No Drawing.Application March 4, 1953, Serial No. 340,377

Claims priority, application Sweden March 5, 1952 3 Claims. (Cl. 51-282)The present invention relates to a method of cleaning and decolorizingshoes and other leather articles, for example smooth shoes and smoothleather coats, mocha shoes, mocha coats, handbags and the like forredyeing, if desired. Old dye, shoe polish and dirt on leather articleshave hitherto been removed by means of a solvent, such as acetone orbenzene, and pumice and the like, and it may take the shoemaker closeupon an hour to clean a pair of shoes. Nor was it thereafter possible toredye the leather in another color than the original one, owing to thefact that in the above-mentioned manner the leather was not thoroughlycleaned and the old grain was not removed. Besides, the surface becameunsuitable even when the article was to be dyed in the original color,due to the fact that the new dye could not penetrate into the leatherbut remained as a layer on the surface, so that the layer of dye thusobtained easily scaled off.

Now it has appeared that shoes and other leather articles, such assmooth shoes, mocha shoes etc. can be cleaned and decolorized forre-dyeing if the surface of the leather is subjected to the action of acurrent of air, the pressure of which varies between 1.25 and 11 kgs/cm.and which contains round-grained sand having a size varying between 0.05and 1.5 mm. When this method is employed, a complete decolorization isobtained, the old grain is removed and the surface of the leather isroughened and will have the same appearance as soft mocha leather, andtherefore it is easily re-dyed.

The sand used must consist of round grains, as for example sea sand.Sand obtained by grinding stone is not adapted for use, as the sharpsand grains will tend to cut off the thin nap which in turn makes theleather less suitable than if sand of round grains is used. The size ofthe grains and the pressure may be varied. If, for example, a stronglyroughened surface is desired, coarse sand and a high pressure shall beused, whereas sand of fine grains and a low pressure will bring about asmooth surface. Thus, it is not possible quite generally to state whatpressures and sizes of the grains are to be preferred. These factors aredetermined by the properties the leather treated is to have, and are forinstance dependent on the degree of dirtiness, the thickness and thequality of the leather, and if a smooth or roughened surface, forexample a mocha-like surface is desired. If, for example, certainportions of a shoe are not to be treated, for example if the shoe has amocha-like as well as a smooth surface, masking tapes, for instance ofpaper coated with rubber, may be used. If, however, these portionscannot be protected by means of masking tape, they may instead be coatedwith a mineral fat, such as Vaseline.

The quantity of sand carried by the current of air is also variable.Thus, if a coarse nap is to be obtained, a smaller quantity of sandshould be used, whereas a finer nap requires a larger quantity.

Furthermore, the size of the opening of the nozzle 2,731,775 PatentedJan. 24, 1956 ICC.

used is of great importance. If a great quantity of sand is to be used,the opening must be large and vice versa. For shoes and leather articlesof the above mentioned kind nozzles are generally used having an openingthe size of which varies from 1 to 6 mm. and preferably from 2 to 4 mm.

If the leather article, for example a shoe, is very old and dry and fullof cracks and wrinkles it is to be preferred before the blasting or thedyeing to make the surface soft by means of some suitable agent, forinstance parafiin oil, castor oil or some fat.

When treating a leather surface on which there are stains, for instancefrom gluten, varnish, tar, resin or the like, there will be such astrong friction heat when the sand strikes such spots that the stainwill spread and the leather may be burned or scorched. However, it hasappeared that this difiiculty is easily overcome, if to the sand usedfor the treatment one or more substances are added which can reduce orremove the friction heat, for example mineral acid salts of alkalimetals and/or alkaline earth metals, for example sodium and potassiumsalts, such as the chlorides, the sulphates, the carbonates, thephosphates and further the corresponding ammonium salts. Sodium chlorideis to be preferred, particularly as it is comparatively cheap and has aneutral reaction. However, although they have alkaline reaction, alsopotassium and sodium carbonate are suitable for this purpose. A salt ofthis kind is used in a quantity varying from 1 to 25% of the weight ofthe sand, but a quantity from 5 to 15% is to be preferred. When a saltof the kind mentioned is added, less friction heat is generated and thestains do not spread but can be removed as easily as old dye and dirt.

The invention is illustrated by the following example:

Example-For cleaning and decolorization for example of old dirty shoes asand blaster of usual construction is used. The nozzle of the sandblaster is conducted vertically towards the leather and the pressureemployed amounts to 4 kgs./crn. whereby the dye and the dirt is removed,and the leather becomes completely clean.

Thereafter the nozzle is pointed obliquely to the leather and a smallerquantity of sand and higher pressure, for example 5 kgs./cn1. areemployed. The sand then cuts through the old grain which is ground awayand the leather now assumes the look and form of fine mocha leather.Owing to the fiutfy surface thus obtained the leather is adapted forredyeing and any colour can be attained. Thus, with a spray gun aniline,latex, methyl alcohol and castor oil can be sprayed between the tinenaps at a pressure of 3.5-4 kgs/cmfl. Then the leather is pressedagainst a rotating brush which rotates at a speed of about 1200-1400revolutions a minute, where by the nap is pressed down and the leatherbecomes smooth. This treatment may be repeated several times. After theleather has become smooth, a collodion dye is sprayed on which mergesinto the basic colour.

By using the abovementioned method old shoes attain the desired colourand the same appearance as new shoes. The dye applied does not scaleoff, as, by the roughening of the leather it has penetrated into thepores of the leather.

The present method is also well adapted to cleaning and decolorizationof mocha leather. As is well-known mocha leather cannot be successfullydry-cleaned but assumes as a result of such cleansing a spotted andflamy appearance, and besides it becomes stiif and brittle. When treatedby means of the method according to the present invention all dirt anddye are removed from the mocha leather which will be given an appearanceas if it were quite new.

If, for example, a mocha shoe is so worn that it cannot be given amocha-like surface without the shoe being ruined (for example by holesappearing), it is yet possible in many cases to make the surface smoothwithout producing holes or other injuries. For this purpose a greatquantity of fine-grained sand and high pressure are used. Afterwards theshoe can be redyed in the manner stated because a very short nap isalways obtained.

When the dyeing has been finished, it is sometimes to be preferred togrind off the leather surface again in order to remove grains which mayhave fastened superficially and which might easily be loosened from thesurface.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

l. A method of cleaning used leather which comprises blasting theleather in dry condition with a current of air at a pressure within therange from 1.25 to 11 kilograms per square centimeter, said current ofair having suspended therein round-grained sand of a size within therange from 0.05 to 1.5 millimeters.

2. A method according to claim 1 in which in addition to the sand thecurrent of air carries a substance of the group consisting of mineralacid salts of alkali metals and alkaline earth metals and ammonium inquantity within the range from 1 to 25% of the weight of the sand.

3. A method according to claim 2 in which the substance is sodiumchloride.

References Cited in the file of this patent UNITED STATES PATENTS1,230,654 Berry June 19, 1917 1,556,261 Stoddard Oct. 6, 1925 2,222,656Erkel Nov. 26, 1940 2,436,928 Kempe Mar. 2, 1948 2,448,316 Lesavoy Aug.31, 1948 2,488,068 Roman Nov. 15, 1949 2,516,222 Lindmark July 25, 1950

